US20230399263A1 - Aluminous sintered product - Google Patents

Aluminous sintered product Download PDF

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US20230399263A1
US20230399263A1 US18/034,879 US202118034879A US2023399263A1 US 20230399263 A1 US20230399263 A1 US 20230399263A1 US 202118034879 A US202118034879 A US 202118034879A US 2023399263 A1 US2023399263 A1 US 2023399263A1
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percentage
alumina
sintered product
mass
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Thibault Champion
Michel Bobo
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Saint Gobain Centre de Recherche et dEtudes Europeen SAS
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Saint Gobain Centre de Recherche et dEtudes Europeen SAS
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    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
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    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B17/00—Forming molten glass by flowing-out, pushing-out, extruding or drawing downwardly or laterally from forming slits or by overflowing over lips
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    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
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    • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
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    • C04B2235/3217—Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
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Definitions

  • the invention relates to an aluminous sintered product, to a process for manufacturing such a product, to a particulate mixture and a starting feedstock that are suitable for this process, and to a preform leading, via sintering, to said aluminous product.
  • fused cast products As described for example in US 2001/0019992, most often comprise an intergranular vitreous phase connecting crystalline grains.
  • a composition developed for manufacturing a fused cast product is therefore not a priori usable for manufacturing a sintered product having the same properties, and vice versa.
  • the sintered products are obtained by mixing appropriate starting materials and then shaping this mixture in the form of a preform and firing said preform at a temperature and for a time that are sufficient to achieve the sintering of said preform.
  • This firing can be performed in firing kilns or else in situ, in the glass furnace for products sold unsintered or unshaped.
  • aluminous products are known to be used in installations for the manufacture of glass articles, in particular in the distribution channels or “feeders”.
  • One aim of the invention is to at least partially address this need.
  • this aim is achieved by means of a particulate mixture consisting of particles the composition and crystallographic structure of which are adapted to form, by heating at 1350° C. for 10 hours, a sintered product having:
  • the particulate mixture may contain a binder in particulate form.
  • the binder is chosen from a hydraulic cement, a resin, a lignosulfonate, a cellulose derivative, dextrin, a gelatin, an alginate, a tylose, pectin, anhydrous phosphoric acid, an aluminum monophosphate, alumina hydrates, an anhydrous sodium silicate, an anhydrous potassium silicate, and mixtures thereof.
  • the particulate mixture may contain a shaping agent in particulate form, preferably selected from a clay, a plasticizer, such as polyethylene glycol (or “PEG”) or polyvinyl alcohol (or “PVA”), a deflocculant, such as an alkali metal polyacrylate, a polycarboxylate, a polysulfonate, a cementitious setting accelerator, a cementitious setting retarder, and a mixture of these agents.
  • a plasticizer such as polyethylene glycol (or “PEG”) or polyvinyl alcohol (or “PVA”)
  • PEG polyethylene glycol
  • PVA polyvinyl alcohol
  • deflocculant such as an alkali metal polyacrylate, a polycarboxylate, a polysulfonate, a cementitious setting accelerator, a cementitious setting retarder, and a mixture of these agents.
  • the particulate mixture may contain fibers, preferably organic fibers, preferably of the vinyl or polypropylene type, preferably in an amount by mass of between 0.01% and 0.1%, preferably in an amount by mass of between 0.01% and 0.03%.
  • the mean length (arithmetic mean) of these fibers is greater than 6 mm, preferably between 18 and 24 mm.
  • the particulate mixture does not contain fibers.
  • a particulate mixture according to the invention may for example be packaged in drums or in bags.
  • the particulate mixture according to the invention preferably comprises
  • a particulate mixture according to the invention advantageously makes it possible to manufacture a sintered product according to the invention, said sintered product having:
  • the sintered product according to the invention exhibits very good behavior in contact with a molten glass, and in particular exhibits good resistance to bubbling and to penetration by the molten glass. In addition, it has good resistance to deformation during sintering.
  • a starting feedstock comprising a particulate mixture according to the invention is put into the form of a preform.
  • the invention also relates to the starting feedstock and the preform.
  • a starting feedstock according to the invention may be packaged in drums.
  • the preform is dry, which facilitates the handling thereof.
  • the invention also relates to a process for manufacturing a sintered product according to the invention, comprising at least the following successive steps:
  • the starting feedstock is shaped in situ, that is to say at the location at which the product according to the invention, in an operating position, is intended to be brought into contact with molten glass.
  • the preform which is preferably dry, is disposed in the operating position, and then sintered in situ, preferably during the rise in temperature of the furnace.
  • the preform is dried, is at least partially machined, is made of a hardened concrete, and is disposed in the operating position, and then sintered in situ, preferably during the rise in temperature of the furnace.
  • the invention also relates to the preform obtained on conclusion of step c) or d) of the manufacturing process according to the invention.
  • a particulate mixture or a sintered product according to the invention also comprises one, and preferably multiple, of the following optional characteristics:
  • the invention lastly relates to a glass production unit, in particular a glass furnace, comprising a part comprising or, preferably, consisting of a sintered product according to the invention, preferably manufactured according to the process according to the invention, and/or, preferably, a preform obtained on conclusion of step c) or d), respectively, of the process according to the invention.
  • FIG. 1 Another characteristic and advantages of the invention will emerge further on reading the detailed description that follows and on examining the appended drawing in which FIG. 1
  • FIG. 1 schematically illustrates a device for measuring the heat distortion.
  • the process for manufacturing a sintered product according to the invention comprises steps a) to e), which are conventional but which are adapted to the invention.
  • the particle size of the particulate mixture is adapted, in particular depending on the shaping in step c).
  • Andreasen or Fuller-Bolomey packing models may be used. Such packing models are described in particular in the work entitled “Trait ⁇ tilde over (e) ⁇ de céramiques et made minéraux” [Treatise on Ceramics and Inorganic Materials], C. A. Jouenne, published by Septima, Paris (1984), pages 403 to 405.
  • the particle size of the particulate mixture is adapted so that the sintered product is a sintered concrete.
  • At least 90% by mass of the particles with a size of less than 50 ⁇ m of the particulate mixture according to the invention have a size of less than 40 ⁇ m, preferably less than 30 ⁇ m, preferably less than 20 ⁇ m, or even less than 10 ⁇ m.
  • the fraction of the particles of the particulate mixture having a size of less than 50 ⁇ m comprises less than 30%, preferably less than 25%, preferably less than 20%, preferably less than 15%, preferably less than 10%, preferably less than 5%, of particles based on beta-alumina, as percentage by mass based on said fraction.
  • the fraction of the particles of the particulate mixture having a size of less than 50 ⁇ m preferably comprises alpha-alumina particles, cement particles and shaping agent particles, preferably alpha-alumina particles, cement particles and deflocculant particles.
  • the particulate mixture contains at least 10% of particles with a size of greater than 2 mm, as percentage by mass.
  • the particulate mixture may have:
  • the particulate mixture according to the invention does not comprise cement.
  • the particulate mixture according to the invention comprises a cement and the starting feedstock does not comprise a liquid binder.
  • the starting feedstock does not comprise a liquid binder.
  • the solvent is preferably water.
  • the amount of solvent, preferably water is greater than 4%, preferably greater than 5%, and/or less than 7%, preferably less than 6%, as percentage by mass relative to the mass of the particulate mixture. If a technique of shaping by uniaxial pressing is used in step c), the amount of solvent, preferably water, is greater than 2%, preferably greater than 3%, and/or less than 6%, preferably less than 5%, as percentage by mass relative to the mass of the particulate mixture.
  • the particulate mixture comprises a hydraulic cement
  • the addition of water activates the hydraulic cement, that is to say causes it to start solidifying.
  • the amount of solvent preferably water
  • the amount of solvent is preferably greater than 3%, preferably greater than 4%, preferably greater than 5%, and preferably less than 9%, preferably less than 8%, preferably less than 7%, as percentage by mass relative to the mass of the particulate mixture.
  • the starting feedstock is conventionally mixed in a mixer.
  • step c) the starting feedstock is shaped.
  • the shaping may comprise an isostatic pressing, slip casting, uniaxial pressing, casting of a gel, vibrocasting or a combination of these techniques.
  • the starting feedstock is poured into a mold.
  • the starting feedstock is poured into a mold where it hardens, in particular via the solidification resulting from the reaction of the hydraulic cement with the solvent, preferably the water.
  • the mold is shaped such that the sintered product has the shape of a block, all the dimensions of which are greater than 1 mm, greater than 5 mm, greater than 5 cm, and all the dimensions of which are preferably less than 500 cm.
  • the mold is shaped such that the sintered product has a mass of greater than 1 kg, greater than 5 kg, greater than 10 kg, or even greater than 100 kg, and/or less than 2500 kg, or even less than 2000 kg.
  • the amounts of oxides, and in particular of alpha-alumina and beta-alumina, and their crystallographic structure are substantially not modified.
  • the preform may thus have:
  • the preform may undergo a drying step, in order to remove a portion of the water that has been used for the shaping.
  • the drying results in a preform having a residual moisture content of less than 2%.
  • a drying step is fully known to those skilled in the art. All drying techniques can be envisaged.
  • step e the preform is sintered so as to obtain a sintered product according to the invention.
  • the sintering is preferably performed at atmospheric pressure, preferably with a stationary temperature phase of a duration greater than 5 hours and/or less than 15 hours, at a temperature of greater than 1100° C. and/or less than 1700° C.
  • Sintering may be carried out in situ, i.e. after the hardened block has been positioned in its operating position, in the glass manufacturing installation.
  • the mold can even be disposed such that after demoulding the hardened block is in its operating position. It is then shaped in situ and at least partly sintered in situ. Shaping in situ makes it possible to manufacture large blocks, which are impossible or difficult to move later.
  • the sintered product preferably comprises more than 98%, preferably more than 99%, preferably substantially 100%, of oxides, based on the mass of the sintered product.
  • the shaping and the sintering are adapted, in known manner, such that:
  • Parts are manufactured according to a process in accordance with the invention.
  • step a the oxide powders and the modified polycarboxylate ether are metered out and mixed so as to form a particulate mixture.
  • step b) the particulate mixture and water are introduced into a mixer. After mixing for a duration of 20 minutes, a starting feedstock is obtained.
  • step c) the starting feedstock is cast into a wooden mold, so as to obtain a preform in the form of a brick having a length equal to 230 mm, a width equal to 115 mm and a thickness equal to 115 mm, and a preform in the form of a bar having a length equal to 500 mm and a cross section equal to 40 mm ⁇ 40 mm.
  • the bar is used, after drying, for characterizing the deformation during sintering.
  • step d after demolding and drying at 110° C. for 24 hours, the preform in the form of a brick is sintered in the following thermal cycle:
  • Table 1 summarizes, for each example, the composition of the particulate mixture in step a) and of the starting feedstock in step b).
  • the chemical analyses are carried out by X-ray fluorescence.
  • Crystallographic analyses are performed on samples reduced to powder, on a Bruker D5000 appliance sold by Bruker, using a Rietveld refinement.
  • the bubbling behavior on contact with molten glass of the sintered products of the examples is evaluated by the following method.
  • Each crucible is filled with 30 grams of a soda-lime glass powder, the median size of which is equal to 1 mm, the maximum size of which is equal to 5 mm, and having the following chemical analysis by mass: SiO 2 : 71.6%, CaO: 12.5%, Al 2 O 3 : 2%, Na 2 O+K 2 O: 12.3%, other oxides: 1.6%.
  • the ratio of the area of the bubbles generated during the test to the area of glass observed can be evaluated with the following nonlimiting method.
  • the slice is then polished in order to make the glass transparent and facilitate observations, said polishing being performed at the least with a 1200 grade paper, preferably with a diamond paste.
  • Images are then acquired with the aid of an optical microscope, a light source illuminating the glass slice from the side opposite the optical microscope (backlighting). This backlighting reveals the bubbles contained in the glass.
  • the focusing, in particular the aperture, is performed such that all the bubbles contained in the part of the glass slice observed appear sharp.
  • the magnification used is the highest possible magnification making it possible to obtain an image corresponding to 0.5 mm 2 of the surface of the glass of the slice, the total number of images being equal to the number of images necessary to be able to observe the entire surface of the glass of the slice, without overlap.
  • each image t is then analyzed using the imageJ software, available on the site http://rsbweb.nih.gov/ij/according to the following method:
  • This ratio characterizes the bubbling behavior of the sintered product on contact with the molten glass.
  • the ability of the molten glass to penetrate into the sintered product is assessed by measuring, after bubbling test and creation of the slice required for the quantification of the bubbling, the mean penetration by the molten glass into the thickness of the walls of the crucible that are in the slice.
  • a bar of length equal to 500 mm and cross section equal to 40 mm ⁇ 40 mm of each example of dry product is disposed in an electric furnace, on two sintered alumina supports of dimensions equal to 40 ⁇ 40 ⁇ 40 mm 3, disposed as shown in FIG. 1 a , the inside distance between said two supports, e, being equal to 400 mm.
  • the deformation during the sintering is the value of the deflection f measured in mm on each bar, as shown in FIG. 1 b.
  • Table 2 summarizes the characteristics obtained after sintering.
  • a measured glass penetration equal to 20 mm means that the glass has passed through the thickness of the base of the crucible.
  • the ratio of the area of bubbles to the area of glass observed, expressed as percentage, is low for the products of examples 2 to 5.
  • the ratio of the area of bubbles to the area of glass observed could not be determined for the product of example 1 because there was not enough glass remaining in the crucible after the test.
  • the mean penetration of the glass into the base of the crucible is lower for the products of example 2 (8% of beta-alumina, mean penetration of the glass into the base of the crucible of 15 mm), of example 3 (17% of beta-alumina, mean penetration of the glass into the base of the crucible of 10 mm), of example 4 (30% of beta-alumina, mean penetration of the glass into the base of the crucible of 3.3 mm) according to invention, and 5 outside of the invention (42% of beta-alumina, mean penetration of the glass into the base of the crucible of 2.8 mm), than that of the product of example 1 outside of the invention (0% of beta-alumina, mean penetration of the glass into the base of the crucible of 20 mm).
  • the deformation during the sintering measured by the deflection f is lower for the product of examples 2 (8% of beta-alumina, deflection f equal to 6 mm), 3 (17% of beta-alumina, deflection f equal to 5.2 mm) and 4 (30% of beta-alumina, deflection f equal to 7.5 mm) according to the invention, than that of the product of example 5 outside of the invention (42% of beta-alumina, deflection f equal to 12 mm).
  • examples 2, 3 and 4 according to the invention are therefore the only ones to exhibit a low degree of bubbling on contact with soda-lime glass, low mean glass penetration, and low deformation during the sintering.
  • the product of example 4 is the product that is preferred among them all.

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  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Structural Engineering (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
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FR2011202A FR3115782B1 (fr) 2020-11-02 2020-11-02 Produit fritte alumineux
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CA1247151A (fr) * 1985-06-24 1988-12-20 Thomas R. Kleeb Composition refractaire resistant a l'abrasion
FR2804425B1 (fr) 2000-01-31 2002-10-11 Produits Refractaires Produits electrofondus a base d'alumine-zircone-silice a microstructure amelioree
WO2001092183A1 (fr) * 2000-05-31 2001-12-06 Asahi Glass Company, Limited Matiere refractaire coulee poreuse contenant beaucoup d'alumine et procede de production correspondant
WO2007065874A1 (fr) * 2005-12-05 2007-06-14 Schott Ag Procede de fabrication de verre plat par la methode de flottage ainsi que levre deversoir (spout lip) utilisee dans la methode de flottage
CN101367665B (zh) * 2008-09-28 2010-12-08 瑞泰科技股份有限公司 烧结α-β氧化铝砖
RU2656647C1 (ru) * 2011-04-13 2018-06-06 Сэнт-Гобэн Керамикс Энд Пластикс, Инк. Огнеупорное изделие, содержащее бета-глинозём
FR2986012B1 (fr) * 2012-01-20 2017-12-01 Saint Gobain Ct Recherches Cuve d'electrolyse.
FR2994177B1 (fr) * 2012-08-01 2014-08-15 Saint Gobain Ct Recherches Particule frittee a base d'alumine
JP6386801B2 (ja) * 2014-06-10 2018-09-05 Ａｇｃセラミックス株式会社 アルミナ溶融鋳造耐火物とその製造方法
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